Dispatch management model

ABSTRACT

A method includes monitoring a system for fault conditions, determining an estimated energy loss based on the fault condition, determining an estimated product loss and/or sales loss based on the fault condition, and scheduling maintenance to correct the fault condition. Maintenance is schedule to correct the fault condition prior to the energy loss and the product loss exceeding maintenance costs.

FIELD

The present teachings relate to refrigeration systems and moreparticularly to a cost/benefit module and a maintenance schedulingmodule of a refrigeration system.

BACKGROUND

Refrigerated and frozen food product travels from processing plants toretailers, where the food product remains on display case shelves forextended periods of time. The display case shelves are typically part ofa refrigeration system for storing and displaying the refrigerated andfrozen food product and must be constantly cooled to ensure maximumproduct life. Retailers attempt to maximize the shelf-life and qualityof the stored food product while concurrently maximizing the efficiencyof the refrigeration system. In so doing, retailers receive a profitthrough sales of quality products while spending a minimum on energycosts associated with product display (i.e., refrigeration, etc.).

Any breakdown in the refrigeration system or variation in performancecan cause food quality issues and negatively impact the profit of theretailer. Therefore, retailers typically monitor refrigeration systemequipment to ensure that the equipment operates at expected levels. Whenthe refrigeration equipment is operating at a reduced capacity, or isnot operating at all, retailers are accustom to immediately calling arepair technician to promptly restore the refrigeration system to normaloperation.

For example, when a retailer notices a refrigeration system fault suchas a condenser fan failure, the retailer typically contacts a repairperson as soon as possible to repair the fan and restore therefrigeration system to normal operation. The retailer usually pays ahigher maintenance premium for an emergency service call due to therequired response time and urgency of the situation (i.e., overtime pay,weekend maintenance, etc.). The added expense associated with emergencyservice is typically justified as emergency maintenance costs do nottypically outweigh the expense associated with loss of the refrigeratedand/or frozen food product, loss of product sales, and/or consumption ofexcess energy.

In addition to the premium associated with emergency service, retailersoften incur higher repair bills due to the frequency in which service isperformed. The fear of spoilage prompts retailers to schedulemaintenance at the first inclining of a fault condition. The reactivenature of such a system results in frequent service calls and, thus,higher overall maintenance costs as repair technicians typically requirea flat fee for simply responding to the call (i.e., driving to theparticular location). Therefore, because retailers are reactive torefrigeration system faults and do not typically have a predictive orcondition-based maintenance schedule in place, most retailers incurhigher-than-necessary maintenance costs.

SUMMARY

A method includes monitoring a system for fault conditions, determiningan estimated energy loss based on the fault condition, determining anestimated product loss and/or sales loss based on the fault condition,and scheduling maintenance to correct the fault condition. Maintenanceis schedule to correct the fault condition prior to the energy loss andthe product loss exceeding maintenance costs.

Further areas of applicability of the present teachings will becomeapparent from the detailed description provided hereinafter. It shouldbe understood that the detailed description and specific examples areintended for purposes of illustration only and are not intended to limitthe scope of the teachings.

BRIEF DESCRIPTION OF THE DRAWINGS

The present teachings will become more fully understood from thedetailed description and the accompanying drawings, wherein:

FIG. 1 is a flowchart of a cost-benefit maintenance module for a systemin accordance with the present teachings; and

FIG. 2 is a flowchart of a maintenance-scheduling module for use withthe cost-benefit module of FIG. 1.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is in no wayintended to limit the teachings, application, or uses.

As used herein, the term module refers to an application specificintegrated circuit (ASIC), an electronic circuit, a processor (shared,dedicated, or group), and memory that execute one or more software orfirmware programs, a combinational logic circuit, and/or other suitablecomponents that provide the described functionality.

With reference to the figures, a maintenance management module 10 isprovided and includes a cost-benefit module 12 and amaintenance-scheduling module 14. The cost-benefit module 12 may be usedto determine an optimum time to service equipment (not shown) based on aparticular fault detected. The cost-benefit module 12 may receiveinformation regarding the particular fault, calculate a time in whichthe fault should be corrected based on an estimated loss, and output amaintenance task to repair the fault within the calculated time. Themaintenance-scheduling module 14 may work in conjunction with thecost-benefit module 12 to bundle maintenance tasks and allow a repairtechnician to correct multiple system faults on a single service calland within regular working hours.

The cost-benefit module 12 may directly monitor a system for systemfaults 16 or may receive an input from a protection and control systemregarding system operating conditions 18. In either of the foregoingsituations 16, 18, the cost-benefit module 12 first determines if asystem fault is detected 20. If a fault is not detected, thecost-benefit module 12 is started anew and is continually looped duringoperation of the system until a fault is detected. If a fault isdetected, the cost-benefit module 12 first determines an energy costassociated with the particular fault 22. It should be understood thatwhile the cost-benefit module 12 will be described as electronicallymonitoring and reporting faults that manual monitoring and reporting offaults (i.e., by way of human interaction) may be used in conjunctionwith, or in place of, such electronic monitoring and reporting.

Energy cost is generally defined as an increase in energy consumptiondue to continued operation of the system under the fault condition. Forexample, in a refrigeration system, if a condenser coil is partiallyblocked, continued operation of the refrigeration system will consumeadditional energy when compared to the same system having a cleancondenser coil. Therefore, the energy cost is generally defined as theadditional cost associated with operating the refrigeration system witha dirty condenser coil when compared operation of the same refrigerationsystem with a clean condenser coil. Energy cost is generally given by:Energy Cost=kWh*Price Per Unit*Time  (Equation 1)

In addition to energy cost, a product loss and/or sales loss due to theparticular fault can be determined 24. Product loss is generally definedas any profit or product lost due to the system fault and can thereforebe represented as a dollar amount. For example, in a refrigerationsystem application, product loss can be generally defined as spoiled ordamaged food product caused by insufficient cooling. Sales loss isgenerally defined as any profit or product lost due to the system faultthat causes a consumer to refrain from purchasing product. Sales lossmay be caused by a product being in an apparent undesirable conditionwhen in fact the product is within a prescribed temperature range. Forexample, a product may have condensation formed thereon caused byinsufficient cooling, which may cause a consumer to refrain frompurchasing the product. Once energy cost and product loss aredetermined, an estimated total loss can be approximated by summingenergy cost and cost of product loss:Estimated Total Loss=Energy Cost+Cost of Product Loss and/or SalesLoss  (Equation 2)

The estimated total loss is used by the cost-benefit module 12 indetermining a maintenance cost associated with the particular faultdetected 26. Maintenance cost is generally defined by the followingequation where labor costs include a repair technician's hourly or dailyservice rate, travel charges include flat service fees (i.e., forresponding to the maintenance request), mileage, and truck-relatedexpenses, and parts cost include any cost associated with replacementparts used in performing the maintenance task:Maintenance Cost=Labor Cost+Travel Charges+Parts Cost  (Equation 3)

In a balanced system with no profit or loss, equipment maintenanceshould be scheduled such that the estimated total loss generally equalsmaintenance cost:Estimated Total Loss=Maintenance Cost  (Equation 4)

If the estimated total loss is generally equal to the maintenance cost,Equation 2 can be substituted into Equation 4 to yield the followingrelationship:Energy Cost+Cost of Product Loss and/or Sales Loss=MaintenanceCost  (Equation 5)

Solving Equation 5 for Energy Cost and substituting Equation 1 intoEquation 5 yields the following relationship:kWh*Price Per Unit*Time=Maintenance Cost−Cost of Product Loss and/orSales Loss  (Equation 6)

Solving Equation 6 for the time element of Equation 1 yields thefollowing relationship:Time=(Maintenance Cost−Cost of Product Loss and/or SalesLoss)/(kWh*Price Per Unit)  (Equation 7)

At this point, the cost-benefit module 12 may determine the energy costas a function of the maintenance cost and product/sales loss usingEquation 6 and can determine a time in which the system fault must becorrected using Equation 7. However, prior to doing so, the energymodule 12 will first determine if the product/sales loss exceedsmaintenance cost 28. If the product/sales loss exceeds maintenance cost,the cost-benefit module 12 declares an emergency maintenance task thatis immediately scheduled by the scheduling module 14 to promptly correctthe system fault and restore the system to normal operation 30. Whenproduct/sales loss exceeds maintenance cost, delaying maintenance is noteconomically sound as the costs associated with product/sales lossoutweigh those associated with correcting the fault (i.e., maintenancecost). Therefore, when product/sales loss exceeds maintenance cost, therequired maintenance should be performed as soon as possible.

Whenever the maintenance cost is lower than the cost of product/salesloss, Equation 7 may yield either a value of zero or a negative number,indicating that the fault should immediately be corrected. If themaintenance cost is greater than the cost of product/sales loss,Equation 7 may yield a positive number, indicating the time in which thefault should be corrected. It should be noted that Equation 7 may stillyield a number that indicates that a fault should immediately becorrected even when the maintenance cost exceeds the cost ofproduct/sales loss. For example, if maintenance cost exceeds the cost ofproduct/sales loss, but the energy consumed per unit is relatively high,Equation 7 will yield a small number indicating that the fault should beimmediately corrected.

For example, in a refrigeration system, if a compressor fault isdetected such that the compressor is no longer able to circulaterefrigerant through the system, the system is not able to provide anycooling effect. The total loss of cooling likely results in a totalproduct loss (i.e., food spoilage). Therefore, the cost-benefit module12 will declare an “emergency” fault and the maintenance-schedulingmodule 14 will promptly respond to the fault condition by immediatelyscheduling maintenance. For such emergency faults, maintenance isscheduled to correct the fault even if additional maintenance costs areincurred, such as overtime costs and weekend service charges to preventproduct loss.

The cost-benefit module 12 delays maintenance for less-urgent or“non-emergency” faults by using equation 7 to determine a repair time inwhich the system fault must be corrected based on energy costs and costof product loss 32. In so doing, the cost-benefit module 12 is able tobalance additional energy costs and cost of product loss associated withthe system fault against the cost of repair. The cost-benefit module 12is able to put off repairing the “non-emergency” fault conditions untileconomically necessary (i.e., when product loss and/or energy costsexceed the maintenance cost). Once the repair time is determined, thecost-benefit module 12 may post a maintenance request in amaintenance-scheduling queue 34, listing the particular fault, thecorrective action, and the time in which the fault must be corrected.

For example, if a refrigeration system experiences a non-emergency faultsuch as a dirty condenser coil during a winter season, it is unlikelythat there is any cost associated with product loss (i.e., cost ofproduct loss is essentially zero). The dirty condenser coil causes therefrigeration system to consume additional energy at a constant rate of10 cents per kWh, assuming that the additional energy consumptionremains constant (i.e., the condenser coil does not become more cloggedover time). The additional 10 center per kWh translates into a cost perunit of $0.1. Therefore, assuming that the maintenance cost to repairthe blocked condenser coil is one-thousand dollars, the time in hours torepair the condenser coil (i.e., the repair time) can be determined byinserting the above variables into Equation 7:Time(hours)=($1000−0)/(10*0.1)

The above relationship yields a repair time of 1000 hours orapproximately 41 days. Therefore, the cost-benefit module 12 will post arepair task in the maintenance-scheduling queue to clean the condensercoil within 41 days.

With particular reference to FIG. 2, the maintenance-scheduling queue iscontinuously monitored by the maintenance-scheduling module 14 so thatemergency tasks are completed immediately and non-emergency tasks arecompleted within the calculated repair time 36. Themaintenance-scheduling module 14 first determines if there are anyemergency repair tasks posted in the maintenance-scheduling queue 38. Ifthere are emergency maintenance tasks in the scheduling queue, themaintenance-scheduling module 14 immediately schedules a repairtechnician to correct the fault 40.

If there are no emergency maintenance tasks posted in themaintenance-scheduling queue, the maintenance-scheduling module 14determines if there are any non-emergency maintenance tasks posted 42.If the maintenance-scheduling queue is empty, the maintenance-schedulingmodule 14 continuously monitors the queue until a maintenance task isposted. However, if non-emergency maintenance tasks are posted in thequeue, the maintenance-scheduling module 14 bundles the non-emergencymaintenance tasks 44 such that like repairs can be completed by a repairtechnician on a single visit. In addition, the scheduling module 14 isalso able to bundle maintenance tasks by an estimated time required tocomplete the task. In so doing, the maintenance-scheduling module 14 isable to bundle maintenance tasks into eight-hour blocks of time and cantherefore minimize overtime and premium rates paid to repairtechnicians.

Bundling repair tasks allows the maintenance-scheduling module 14 tocontact a repair technician to correct more than one fault condition,rather than call a repair technician each time a fault condition isdetected. In so doing, the maintenance-scheduling module 14 is able toreduce maintenance costs by reducing the number of individual servicecalls.

Once the maintenance tasks are bundled, the maintenance-schedulingmodule 14 is able to schedule repair at an inexpensive and convenienttime. Inexpensive repairs can be accomplished if all bundled repairs areaccomplished during a single service call or if non-emergency repairsare completed while a repair technician is already on-site. Therefore,once the maintenance tasks are bundled, the maintenance-schedulingmodule 14 may determine if a repair technician is on-site and able torepair additional emergency or non-emergency maintenance tasks in themaintenance-scheduling queue 46.

If a repair technician is on-site to repair an emergency fault, themaintenance-scheduling module 14 is able to scan themaintenance-scheduling queue to determine if there are other emergencyor non-emergency maintenance tasks that can be accomplished while therepair technician is on-site. For example, in a refrigeration system, ifa repair technician is called to repair a failed compressor motor (i.e.,an emergency fault) the maintenance-scheduling module 14 may scan themaintenance-scheduling queue to determine if there are other bundledrepair tasks (i.e., emergency or non-emergency) that the technician canalso repair while on-site 48. In so doing, the maintenance-schedulingmodule 14 is able to reduce maintenance costs by completing multipletasks during one service call.

If a technician is not on-site, and there are maintenance tasks in themaintenance-scheduling queue, the maintenance-scheduling module 14 willschedule maintenance for those faults that are almost at the calculatedrepair date 50. In addition, the maintenance-scheduling module 14 willbundle those maintenance tasks that can be accomplished with those thatare almost at the calculated repair date and complete these additionalmaintenance tasks during the same service call. In so doing, themaintenance-scheduling module 14 is able to reduce costs associated withmultiple trips to the same location by repair technicians and is able toensure that the repairs are completed before product loss.

The description of the teachings is merely exemplary in nature and,thus, variations that do not depart from the gist of the teachings areintended to be within the scope of the teachings. Such variations arenot to be regarded as a departure from the spirit and scope of theteachings.

1. A method comprising: monitoring a system for fault conditions;determining a maintenance cost to correct said fault condition;determining a monetary value of said fault condition; comparing saidmaintenance cost to said monetary value; and scheduling maintenancebased on said comparison.
 2. The method of claim 1, wherein saiddetermining a monetary value includes determining at least one of anadditional energy cost associated with said fault condition, a productloss associated with said fault condition, and a sales loss associatedwith said fault condition.
 3. The method of claim 1, further comprisingperforming said maintenance if said monetary value exceeds saidmaintenance cost.
 4. The method of claim 1, wherein said schedulingincludes listing said maintenance with all other maintenance requests.5. The method of claim 4, further comprising bundling said maintenancewith said other maintenance requests based on said comparison.
 6. Themethod of claim 5, further comprising completing said bundledmaintenance at one service call.
 7. The method of claim 1, wherein saidmonitoring includes electronic monitoring.
 8. The method of claim 1,wherein said monitoring includes manual monitoring.
 9. A methodcomprising: monitoring a system for fault conditions; determining anenergy cost based on said fault condition; determining a product costbased on said fault condition; and determining a maintenance cost basedon said fault condition; and determining a time in which to correct saidfault condition based on said energy cost, said product cost, and saidmaintenance cost.
 10. The method of claim 9, wherein said product costdetermination includes determining product lost due to said faultcondition and sales lost due to said fault condition.
 11. The method ofclaim 9, wherein said maintenance cost determination includesdetermining labor cost, parts cost, and travel time associated withcorrecting said fault condition.
 12. The method of claim 9, wherein saidtime determination includes subtracting said product cost from saidmaintenance cost.
 13. The method of claim 12, further comprisingscheduling maintenance to correct said fault condition if saidsubtraction yields a time value equal to, or less than, zero.
 14. Themethod of claim 12, further comprising delaying maintenance to correctsaid fault condition if said subtraction yields a time value greaterthan zero, said time value indicating a time in which to complete saidmaintenance.
 15. The method of claim 12, further comprising dividing thedifference between maintenance cost and product cost by said energycost.
 16. The method of claim 15, further comprising schedulingmaintenance to correct said fault condition if a result of said divisionyields a time value that is less than a predetermined time value. 17.The method of claim 15, further comprising delaying maintenance tocorrect said fault condition if said division yields a time valuegreater than a predetermined time value, said time value indicating atime in which to complete said maintenance.
 18. The method of claim 9,wherein said monitoring includes electronic monitoring.
 19. The methodof claim 9, wherein said monitoring includes manual monitoring.